1. Field of the Invention
The present invention relates to cooking devices in general, and especially relates to built-in cooking devices such as microwave ovens built into furniture and cabinets.
2. Description of the Related Art
A large number of cooking devices such as microwave ovens with an open/close door disposed on a front side thereof have been proposed, but on the other hand, another type of cooking devices having a drawer integrally formed with a door that can be drawn out to the front side of the device has also been proposed. The drawer type cooking devices can suitably be applied to relatively large-scale structures, so that they are considered as cooking devices constituting a portion of fitted kitchen or designed kitchens. Reflecting the recent systemization and increase in size of kitchens, cooking devices have also been diversified and unitized, and various cooking devices being combined with cook tops, drawer-type microwave ovens, electric ovens and so on and built into kitchens are provided. Built-in cooking devices are suitably applied to kitchen structures where a large number of cooking equipment are arranged three-dimensionally, since built-in devices can be built into areas below the counter top of the kitchen so as not to occupy the space above the countertop. Therefore, drawer type cooking devices are considered as one type of cooking apparatuses that constitute fitted kitchens or designed kitchens, and the use of such drawer type kitchen devices is expanding recently especially in the United States.
The present applicant has proposed a drawer type microwave oven which is a type of a drawer type cooking device, wherein the microwave oven comprises a cooking device body including a heating chamber, a drawer body disposed movably within the cooking device body so as to be drawn out from within the heating chamber of the cooking device body, and a slide mechanism for moving the drawer body within the cooking device body, wherein the slide mechanism is disposed outside the heating chamber, so as to enable the slide mechanism to be formed without using members or materials having high heat resistance and flame resistance, and to prevent the occurrence of discharge failure caused by microwave (patent document 1: Japanese patent application laid-open publication No. 2005-221081). According to the drawer type cooking device, the loading portion for loading the object to be heated in the heating chamber can be drawn out together with the door, so as to eliminate the need to form the slide mechanisms using components or materials having high heat resistance and flame resistance, and to prevent the occurrence of microwave discharge failure caused by microwave.
Traditional cooking devices on countertop are almost without exception supplied with air inlet and outlet over back panel and side panels of the outer cabinet, taking in air through air inlet for the purpose of cooling electrical components and others, and discharging through air outlet hot air with vapor emitting from foods cooked to be scattered into the thin kitchen air. Such configuration in design to place such air inlet and outlet over insignificant areas of the cabinet to counterpart inner configurations requires only ordinary engineering skills and practices.
On the other hand, built-in cooking devices, especially such as shown in the present applicant's patent document 1 above, are allowed to take in and discharge air only by way of limited square inches that could be spared apparently on the front surface, forcing severe restrictions on specialists in the trade to decide upon cooking device configurations. Based on such restrictions arising from majoring in built-in construction, the present applicant has proposed a drawer type cooking device as a built-in kitchen equipment to be built into a cabinet, wherein an air inlet portion and an air outlet portion are collectively disposed on a lower end portion on the front side of the device to thereby improve the efficiency of intake and discharge of air, improve the efficiency of cooling electric components and discharge of inside air, and to relieve the limitations of design and arrangement of the cooking device (patent document 2: Japanese patent application laid-open publication No. 2006-223337).
The concept of air flow according to the air inlet and outlet system according to the above-mentioned drawer type cooking device is as illustrated in FIG. 5. Further, FIGS. 6A and 6B show the arrangement of electric components at a depth portion of the prior art built-in cooking device, wherein FIG. 6A is a right side view and FIG. 6B is a rear view thereof. A louver of the air inlet and outlet grill is disposed to cover the whole width of the cooking device body 51 at the lower front side portion of the cooking device body 51, wherein the left end portion of the front side air inlet and outlet grill is formed as an air inlet port 63. A lower side portion 59 arranged below the heating, chamber 53 of the cooking device body 51 constitutes a bottom surface air inlet and outlet duct structure, wherein the left end portion of the bottom surface air inlet and outlet duct corresponding to the front side air inlet port 63 is formed as an air inlet portion 60. When a cooling fan 56 within the electric component chamber disposed at a rear portion of the cooking device body 51 is activated, cooling air F1 is taken in via the front side air inlet port 63 through the air inlet portion 60, reaches a depth portion chamber at a rear side of a depth wall of the heating chamber 53 of the cooking device body 1, and is further blown into the interior of the cooking device body 51 by the cooling fan 56. In other words, the built-in drawer type cooking device has a front-side concentrated air inlet and outlet grill, and an inlet and outlet air blow duct layer structure formed on the bottom side thereof.
One portion of the blow out air flow (air flow F3) from the cooling fan cools an electric component (magnetron 54), and then flows through an opening portion formed on the depth wall surface of the heating chamber 53 into the heating chamber 53 (F5), passes the interior of the heating chamber 53, and then flows through an opening portion disposed on the front side of the heating chamber into a ceiling panel air outlet duct 66 (F6). The ceiling panel air outlet duct 66 is laid horizontally toward the depth of the product on the outer side of the ceiling panel of the heating chamber (first portion 66a), and at the portion where the heating chamber ceiling panel is ended, it is bent toward the right and laid horizontally (second portion 66b), and then at the right end of the heating chamber, it is laid to bend down perpendicularly to enable air to flow into a vertical duct 67 disposed on the right end (F7 through F9). The discharged air is finally passed through an air outlet duct 61 on the right end of the bottom surface air inlet and outlet duct, and blows out to the exterior through the right end air outlet port 64 of the front side air inlet and outlet grill (F10, F11). The other air flow F4 from the cooling fan cools the electric component (high pressure transformer 55) disposed within the electric component chamber (F12), passes through the air outlet duct 62 disposed at the center of the bottom surface air inlet and outlet duct, and is discharged to the exterior through the center air outlet port 65 of the front inlet and outlet grill (F13, F14). As described, the air outlet duct 61 through which hot air containing vapor from the heating chamber 53 passes is distanced from the air inlet duct 60 through which cool air passes, according to which dew condensation caused by cooling of hot air can be prevented.
It is essentially rational to discharge the hot outlet air flow from the upper area of the cooking device, but since the air will be discharged toward the user, such arrangement cannot be adopted in practice. Further, if the air is discharged through a louver disposed on the lower portion of the cooking device, the hot outlet air flow will be blown out toward the user's legs. Therefore, the prior art drawer type cooking device proposes an arrangement in which an air outlet duct with a louver independently from the door is disposed, which requires an independent area for inlet air and outlet air to be formed within the limited height of the device.
However, according to the above-mentioned drawer type cooking device, the air outlet path becomes long, and the duct structure, especially the duct structure passing through the interior of the heating chamber, becomes complex and the flow path resistance (pressure loss caused by duct resistance) is increased. As a result, a cooling fan having a high air blow performance is required, by which the product costs and operation costs of the cooling fan are increased. Further, in order to push out the air from within the heating chamber, the pressure within the heating chambers turns to high static pressure, so that vapor may easily leak through the clearance formed at the door from within the heating chamber. If the prevention of microwave leakages is highly prioritized, vapor leak may occur from the very fine clearances between the welded portions of the door, causing dew condensation. Since the duct also has may joints, vapor may leak through the joints and cause dew condensation. Further, built-in devices must be placed in limited setting spaces having restricted heights, but since the lower duct and the louver portion take up a certain height, the height for ensuring independent inlet and outlet area had to be sacrificed and taken from the inner space of the cooking device.
As described, according to the built-in drawer type cooking device with a front-side concentrated air inlet and outlet structure, the inlet and outlet air blow duct layer structure is formed on the bottom side of the device, so that the air blow path becomes long, leading to problems such as increase of fan load, deterioration of space utilization efficiency, and reduction of vertical compressive strength caused by the duct (damage caused by impact during shipping of product). Moreover, the air inlet and outlet grill disposed on the lower side of the front surface of the device deteriorates the front side design of the device. Furthermore, according to this arrangement, it is difficult to prevent short circuit of the inlet and outlet air, that is, to prevent the high-temperature outlet air from mixing with the inlet cool air flowing adjacent to the outlet air, according to which the inlet air temperature becomes higher than room temperature.
Patent document 3 (Japanese patent application laid-open publication No. 2002-228163) discloses an attachment panel for a cooking device, comprising forming air blow spaces on the upper portion and the lower portion of the microwave oven being built into a closed space in a furniture instead of being placed in the open space on a counter top, forming an air inlet and outlet opening on a front side of the air blow space, and using a build-in kit for taking in air from and discharging air into the closed space, wherein the air discharged from the lower portion of the front side of the oven is directed downward so as to prevent hot air from blowing directly toward the body of the user.
If the air inlet and the air outlet of the microwave oven are separated vertically into upper and lower areas, the object of preventing hot air from blowing toward the user can be achieved simply by directing the outlet air to flow downward. However, when air is taken in and discharged from adjacent portions on the lower area on the front side, a problem occurs in which the discharged hot air is sucked in through the air inlet and causes short circuit. Therefore, it is necessary not only to improve the arrangement of the attachment panel of the cooking device but also to set the air blow speed of the outlet air, and to improve the arrangements of the inlet port and the outlet port.
The problem to be solved according to the built-in cooking device is to eliminate the inlet and outlet air blow duct layer structure formed on the bottom side of the device, and to alter the air outlet structure for discharging the inside air containing heat and vapor generated during cooking of an object to be cooked to the exterior, so as to form an air inlet and outlet structure capable of blowing air using the clearance between the warm wall surface of the heating chamber and the components disposed inside the cooking device body.
The object of the present invention is to provide a built-in cooking device in which an air outlet duct is formed along the warm wall surface of the heating chamber, to thereby prevent vapor from being cooled rapidly and causing dew condensation.